Simplistic MosFET HV Shunt Regs

[Salas]

What were the conditions of original failure? Was it hooked up to something and failed at a point? What was the raw-reg-load configuration? Input & output Mosfet Vgs how they check out?

 

[merlin el mago]

Was used in the 26 preamp. Raw B+ 335V. CCS adjusted for 30mA.

 

[vgeorge]

335V before the reg for a 26 pre? how much voltage drop?

 

[merlin el mago]

Exactly 322V, I use 250V tx (LCLC) + input choke 10H 100mA + 200uF + choke 10H 100mA + 200uF.

I have other tx of 125V, will be better to use it?

 

[merlin el mago]

CCS working OK

 

[RollE2k]

When i shorted my SSHV2, the CCS worked fine with low voltage (12v) applied for testing - but as soon as i connected my 200V B+ it didnt work at all.. so i had to replace the first DN2540 in the CCS cascode.

 

[merlin el mago]

Appears to be Q1 DN2540 don't like the high input voltage, literally exploited.

 

[merlin el mago]

When i shorted my SSHV2, the CCS worked fine with low voltage (12v) applied for testing - but as soon as i connected my 200V B+ it didnt work at all.. so i had to replace the first DN2540 in the CCS cascode.

My power transformer is 100VA rated and isn't the first time the first DN2540 blowed

 

[merlin el mago]

D5 & D6 near DN2540 also gone...

 

[Ionmw]

Hi Salas,

What is the real BW of your control loop?Any measurements available? I just found your thread, did not read all 5500 replies. Sorry.

Do you think is a good idea to attempt to tasking your regulated PS to deliver 2Adc+/-200mAac into an 1MHz BW audio current amplifier with THS+N <1mA into 16Ohms at160Vdc? My amplifier project is a Class A Circlotron and for example asks the PS for supplying this current(!) waveform (constant voltage) at 100KHz:

An externally hosted image should be here but it was not working when we last tested it.

The 100KHz is max fundamental frequency so the needed relevant harmonics will reach up to 1MHz. So, being part of circlotron's signal path, the PS is asked to correctly supply up to 0.7A/us during these transients.
At less than 5KHz operation I will ask the PS to deliver 2Abias +/-1Asignal (I saw in first pages how to modify your schematic for this, big thanks!), but 0.7A/us condition still remains.

Summing up, your regulated PS looks to me very feasible for a Class A circlotron. It offers a tradeoff: the weight&size for cooling vs weight&size of capacitor bank. A very good trade in my opinion. It is not quite simple to build it but it looks capable. With dedicated output capacitors I hope to reach a firm control of harmonics up to 1MHz. The Circlotron's load is of course inductive. I hope the capacitor bank will not interfere with BW of regulation. What do you think, does it fly?
Any help will be appreciated. Thanks!

 

[merlin el mago]

My power tx are to 125VAC 100VA in series, I guess is enough for 26 preamp target 150VDC?

 

[merlin el mago]

Q5 & Q6 gone.

 

[merlin el mago]

My power tx are two 125VAC 100VA in series, I guess is enough for 26 preamp target 150VDC?

 

[Salas]

Appears to be Q1 DN2540 don't like the high input voltage, literally exploited.

Some very strong transient peak must be happening or a great oscillation when connected to that raw supply and powering up. This kind of cracked open DN2540 400V device damage looks too violent.

 

[Salas]

Hi Salas,
What is the real BW of your control loop?Any measurements available? I just found your thread, did not read all 5500 replies. Sorry.

-3dB at 25kHz open loop and -16dB at 100kHz open loop (for SSHV2 simulated)

 

[Ionmw]

Hi Salas,
great, not shabby at all! Finally something in the ball park.What detail of component or module you think is most critical for increasing this parameter?
What would be the max. expected value (PS still nice behaving) for current slewrate capability assuming 2Adc at 160V?
Thanks,

-3dB at 25kHz open loop and -16dB at 100kHz open loop (for SSHV2 simulated)

 

[merlin el mago]

Some very strong transient peak must be happening or a great oscillation when connected to that raw supply and powering up. This kind of cracked open DN25540 400V device damage looks too violent.

Other one!!!!

 

[merlin el mago]

Attached power transformer & chokes specs.

 

[vgeorge]

I have a #26 pre with dual SSHV2 I made point to point and working fine for years. Never did blow anything.
The transformer you have has to much voltage for 150 Vout. Still you are not telling us your voltage drop, and rectifier schematic (choke or capacitor input, rectifier etc) in order to help you.

 

[merlin el mago]

Exactly 322V, I use 250V tx (LCLC) + input choke 10H 100mA + 200uF + choke 10H 100mA + 200uF.

I have other tx of 125V, will be better to use it?

I have a #26 pre with dual SSHV2 I made point to point and working fine for years. Never did blow anything.
The transformer you have has to much voltage for 150 Vout. Still you are not telling us your voltage drop, and rectifier schematic (choke or capacitor input, rectifier etc) in order to help you.

Rectifier hybrid Graetz AZ1 + two UF4007 (Between power transformer and the AZ1 one 100 ohms resistor.

Now only one 125VAC, attached Vout pic.